Opened Pool 2 days ago - OCLT

jdlw

Active member
Background:
Hi! Our pool was opened Tuesday afternoon and the pool people dumped some liquid chlorine in. When I did the first chlorine test Tuesday evening, I was surprised that CC was only 0.5 (with FC 14ppm) after the long winter. I attributed it to the fact that it's still cold? After cleaning worms/dirt out, I did an OCLT test last night.

Last night, FC was 11.5 and CC was 0.5 (one drop). I got tied up this morning so I couldn't get the water until 10:15pm, but FC was 10.5 and CC was 0.5. It seems too easy to get through the winter without having to SLAM (CYA is 70 so the FC wasn't at SLAM levels) so I tried to validate by doing a 25ml test and got FC=10.8 and CC=0.4

QUESTIONS:

-I think I read that the chemical regents are good for a year, right? I used last year's product, which I got approx 10 months ago, I believe.
-When doing a 25ml chlorine test, do I still use a heaping spoonful of the R0870 and 5 drops of R0003 or should I be increasing them 2.5times?
-"Passing" the OCLT is if CC is under 0.5 and passing if it's over 0.5. But what if you are doing the 10ml test and it is EQUAL to 0.5-is that considered passing?
-Is it possible that there is bacteria or organic matter that is "sleeping" because the water is cold but that it will come in a vengeance week when temperatures warm up to the 70s?

Thanks
 
Last edited:

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
It sounds as though you did good to open before the water temps increased. :goodjob: As we always say, the sooner the better. I see no reason to suspect the reagents. Your reagents should still be fine if they were stored in a cool, dry location away from sunlight. Could bacteria be in the water? Sure, but the amount and it activity would surely be slowed-down in the cooler water. By maintaining an elevated FC level you are helping to neutralize that material early. The cold water is in your favor.

As for the OCLT, it's all about the FC loss. Regardless of which water sample size you use (5ml, 10ml, 25ml) as long as you don't lose more than 1 ppm of FC overnight you've passed. The CC reading is part of the SLAM criteria, but not the OCLT specifically. Pool School - Perform the Overnight FC Loss Test (OCLT)

Hope that helps.
 

jdlw

Active member
Thanks for the answers...it just seems too easy to have my pool in balance already! Especially since all that "food" (boatloads of worms and quite a bit of dirt) had accumulated in the water (well, other than pH which will likely need tweaking and always gives me trouble because my alkalinity is already at the low end of the range...but that's a problem I always have). So I guess I can let the chlorine drift down to targeted levels of approximately 6ppm.

Thanks!
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
It appears your closing process and opening while water is still chilly helped prevent the propagation of organic matter - either from algae or decay of insects. Take pride in the fact you don't have a swamp to deal with. You've passed OCLTs already, so if you chose to let the FC drift to your normal range that's reasonable while you continue to vacuum and remove any remnants of winter. As the water temps increase, if you ever sense something is wrong, you have the tools to do an OCLT and evaluate the possible need for a SLAM or other actions. Enjoy!
 

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